The distribution of Bombus inexspectatus is confined and discrete. The species lives in the Cordillera Cantabrica and on the southern side of the southern Alps. It is also likely present in the Pyrenees, although no valid observation has yet been reported from these mountains (the specimens reported by Ornosa Gallego, 1984, have all been invalidated and revised as ruderarius by L. Castro). This distribution is clearly relict.
B. inexspectatus is very uncommon : Yarrow (1970) reports 36 specimens only among a sample of 10000 bumblebees collected in its Cantabrian locations. Quite clearly, in the absence of such thorough samplings, the species will remain undetected.
B. inexspectatus is a workerless species that inquilines B. ruderarius.
P. Rasmont